Process of filtration.



J. M. NEIL. PROCESS OF FILTRATION.

APPLICATION FILED JAN. 26, 1912.

1,03,455, Patented Nov. 5, 1912.

JAMES MILLAR NEIL, F TORONTO, ONTARIO, CANADA.

, PROCESS OF FILTRATION.

I To all whom it may concern:

Be it known that I, J AMES MILLAR NEIL,

of Toronto, in the county of York, Province of Ontario, Dominion of Canada, have invented certain new and useful Improvements in Processes of Filtration; and I hereby declare that the following is a full, clear, and exact description thereof. This invention is a'novel improvement in methods of filtration, its object being to effect the separation of liquids from solids and solids from liquids more quickly, efficiently and economically than can be done by decantation or by the methods of filtrat-ion heretofore practiced.

use in separating solutions containing precious metals from slimes in cyanidation processes; in separating solutions containing soda'from wood pulp; in separating solutions containing, alkali from caustic lime.

mud; and in many other-arts in which decantation or filtration is or may be used for the separation and recovery of liquids from solids, or of solids from liquids.

The mixture to be separated-which consists of liquids and solids in suspension therein-may beintroduoed into a suitable tank, wherein it should be continually agitated, preferably by withdrawing it from the bottom of the tank and discharging it into the upper part thereof by a suitable pump and connections. The liquor is then separated from the suspended solids in the mixture in the tank, while in agitation; by passing the liquor through a separating medium covered with a filtering substance or cloth permeable by such. liquid but impermeable to the solids, which latter collect on the face of such separatingmedium. Preferably I employ a hollow filtering member, such for example as is shown and described-in Patent No. 7

her, 1903, or No. 955,660 of April 19,1910, which will permit the clear liquid: to pass,

but will not permit the passage of the. suspended solids. This separating medium should be completely submerged in the mixture being treated. The interior of said separating medium'is connected to a suit able'apparatu's or a suction inside of -rranddlffiw the clear meable VFHIFOfthe separating medium into the interior thereof, and discharge the liq uid into any suitable receiver. i

pump adapted to create Specification of Letters Patent.

Application filed January 26, 1912. Serial No. 673,599.

The invention is particularly adapted for 7 4.8,088 of Decemthe separating medium; liquid ,through the perrating medium until a coating Pateiited Nov. 5, 1912.

By reason of the suction in the separating medium particles of the ed in the mixture will be drawn toward the separating medium and will adhere to and coat the outer sides thereof, and impede the drawing off of the clear liquid through the separating medium, and when such coating becomes so thick as to stop or retard the passage of the liquid through the separating medium it has heretofore been necessary to separate the medium from the mixture, and remove the coating from the separating medium; which cleansing operation results in great loss of time in the operation of the apparatus and a corresponding reduction in the outputthereof. For example; in the treatment of slinies, etc. in the cyanide processes for the extraction of precious metals by the known vacuum filtering systems, in many instances the nature of the ores, minerals, etc., undergoing treatment make it impossible to obtain practically satisfactory as the cakes or layers form on the separating mediumso rapidly;that it has heretofore been necessary to frequently remove and cleanse the separating medium, whereby under existing practice the process of filtration is seriously interrupted and retarded. In order to avoid the necessity of such frequent separating and cleaning of the separating medium; and to enable the filtering operation to be continued indefinitely, I at intervals momentarily stop the suction and send a reverse current or pressure outwardly through the separating medium thereby .throwing the deposits or coating on the separating medium back into the mixture while the separating medium remains submerged therein; and this reversal of current clears the separating medium and enables me to immediately resume the suction; and by intermitting the'suction' periods with throwoff periods I am enabled to Withdraw the clear liquid from the mixture until the mixture in'the tank becomes so thick that it is desirable to remove some of the solids therefrom. t 1

t In carrying out my invention'the filter-mg operation is preferably performed as follows: To commence the process the mixture is preferablyrun into a tank and. agitated, while the separating medium is submerged therein; then the clear liquor is drawn from the mixture in the tank through the sepaof solids adsolids suspends and economical operating results heres to the medium suflicient to unduly re- ,tard the flow; then, momentarily, the drawing operation is stopped and a current of air or liquor forced back through the separating medium, thereby loosening or throwing o the coating thereon into the tank; then the suction is immediately resumed until another retarding coating has formed on the separating medium; then this coating is thrown 0E as above; and such suction and pressure operations may be repeated as often as may be desirable, and enable the process of filtration to be carried on almost continuously until it becomes desirable to remove some or all ofthe solids from the tank; and at the same time enables the mixture to be thickened to any desired consistency.

When used in cyanidin processes my vention greatly increases t apparatus in separating and removing the solution from the slimes and enables the separating operation to be carried on for longer periods than under existing methods, thereby increasing the daily capacity of the appw ratus. It also facilitates the handling of materials which interfere with the efficiency of filtering operations as heretofore conducted. This novel method of operation when applied to the well known portable suction filter system enables greater quantities of solution to be handled through the submerged separating medium before removing it from the solution tank to the Wash tank with the cake attached; or when applied to the well known stationary filter system before emptying the solution tank Y in order to render the same available as a through the separating medium thereby wash tank.

My invention is particularly valuable in the treatment of slimes from which the solution; has only been partially removed. Instead of retaining the cake on the separating medium by suction and washing same to recover further solution by drawing barren solution or water through it, (either in a separate wash tank as in the movable sys tem, or in the tank from which the solution has been removed as in the stationary sys-- tem), I may throw ofi the cake into the wash tank containing barren solution or water and thoroughly agitate the same, and then draw the barren solution or wash water again forming a cake. These 0 erations may be repeated as often as may e found necessary, in order to completely free the slimes from solution.

In the movable systemof filtration two or more tanks may be used and the cake or layer formed on the separating medium may be periodically removed or carried over from tank to tank for more eflicient washing; in

such cases my invention enables the filtratlon process in the first or solution tank to be harried on indefinitely and practically e efliciency of the without interruption, while the washing of the separated material by weak solution or water can be carried on independently in one or more separate tanks;

When used for example in the recovery of soda from caustic lime mud, my process eliminates the roduction of enormous vol umes of weak iiquors of varying strengths, such as are produced by the present known processes; which solutions have to be evapand necessitate the employment of large storage tanks, and large and expensive evaporating apparatus; and also enables the filtering process to be continued almost indefinitely between stoppages for cleaning the filter, as by my process the clear liquor is withdrawn of practically uniform strength, while the solids simply accumulate in the tank.

The accompanying drawings represent diagrammaticall an apparatus which might be employed in t e performance of my process.

In said drawings: Figure 1 is a conventional diagrammatic elevation of thefiltr'ation apparatus. Fig. 2 is a detail sectional view through one of the separating units.

In said drawings, 1 represents a tank into which the waste liquors or sewage may be discharged or collected from the works, and from which the liquid to be filtered can be discharged into a tank 2, wherein it may be continually agitated, for example by withdrawing it from the bottom of the tank through a pipe 2 to a suitable pump 2 and discharging it again into the upper part of the ,tank through a pipe 2. i

3. represents a hollow filtering member, (such for example as is shown and described in Patent No. 748,088 of .December 29, 1903, or No. 955,660 of April 19, 1910) which will permit clear liquid to pass, but will not permit the passage, of the suspended solids.

' This filtering member 3 should be completely submerged in the liquid in tank 2. The interior of this filterlng member '3 is con-. nected by a pipe 4: to an apparatus orpuinp r, adapted to create a suction inside of the filtering member 3, and draw the clear liquid through the permeable walls of the filtering orated beforethey can be economically used;

member into the interior thereof, and thence V through pipe 4 to pump 43; from which it may be discharged through a pipe 4 into any suitable receiverzk' at I claim is:

1. The process of separating liquors from a solid matters in suspension therein, consisting in passing the clear liquor through a separating medium submerged therein, thereby causing thesuspended solids to adhere to said separating medium," then momentarily suspending the drawing operation and reversing the current through the-separating medium to throw the adhering solids 1 01f said separating medium; and repeating throw ofi such coating; then resuming the such operations until it is desired to remove suction until the medium is again coated; 35 the solids. then again throwing off the coating; and 2. The process of separating liquid from alternating such suction and throwing off solid matters held in suspension therein, conoperations until it is desired to remove the sisti'ng in alternately passing the clear liqsolids.- uid through a separating medium submerged 5. The process of separating liquids from 40 in the liquid to cause the suspended solids solid matters in suspension therein, conto adhere thereto, and then momentarily sisting in immersing a separating medium reversing the current through the separatpervious to the liquid and impervious to ing medium to throw the solids off said the suspended solids in a tank containing medium, 7 while the latter remains suba mixture of the liquid and solids, agitat- 45 merged. v ing the mixture, then withdrawing, by suc- 3. The process of separating solid mattion, the clear liquid from the mixture ters from liquids in a mixture thereof, con through said separating medium, until a sistingin immersing in the mixture. a sepacoating of the suspended solids has adhered rating medium pervious to the liquid and, to the said medium: then reversing the cur- 6O impervious to the solids then alternately rent momentarily. through the medium to withdrawing the clear' li'quor through said throw the coating ofl said medium while still separating medium, thereby causing a coatsubmerged; and repeating such operations ing of the suspended solids to adhere therein alternation until it is desired to remove to, and momentarily reversing the current the solids; then separating the said medium 5 to throw such coating ofl said separating from the said mixture while coated, and medium while still submerged. discharging the coating on said separating 4. The herein described process of se amedium outside the tank. rating liquids from solids in suspension In testimony that I claim the foregoing therein, consisting in separating the sus as my own, I afiix my signature in presence 60 pended solids bfrorin the cleailr liquor 1while of two witnesses. in agitation; y rawing t e c ear i uor through a pervious separating medium, iintil JAMES MILLAR NEIL said medium is coated with the suspended Witnesses: solids; then momentarily reversing the cur- RUSSELL H. HAWK, rent through the separating medium to GRAoriF. NiEMANN. 

